Yurt, the Silent Chief is a deadly assassin whose only business in Boletaria is to aid in the misdeeds of his accomplice, the enigmatic Mephistopheles, and kill all those who have learned the ways of Soul Arts.

Tendency Events:

Special:

Yurt must be rescued from a cage in World 3-2 to be available. He is near the first tower with the praying prisoners. Follow the colored Augites of Guidance, which you can see from the top of that tower, and you will find his cage.

Assassinations:

If the player rescues Yurt, the next time entering the Nexus after defeating a boss there will be two unnamed corpses on the ground. One is on the outer stairs visible from near Boldwin, and the other is at the second level near the top of the stairs. However, Yurt will roam on the platform where you freed him until a demon is actually killed, so you can safely come back to kill him even after leaving the 3-2 stage with the nearby Shard of Archstone or via Evacuate.

If he is left alone from this point, Yurt will begin killing other named NPCs around Nexus in the following order.

Two non-NPC bodies are first discovered (one on steps near Boldwin, the other one level up)

After killing these NPCs, Yurt's bloodlust seems quenched and he will not kill any more NPCs. If you go talk to him after at least two NPC's are dead, he will explain that he is 'Yurt, The Silent Chief' and say "My work in Boletaria is almost done. I have murdered every human left, except for one…" Then he will turn hostile.1

Yurt will only make one kill after a boss is defeated. He will not have made a kill if you return to the Nexus without having defeated a boss.

These NPCs will not respawn until the player begins a NG+

In order to prevent this, kill him immediately upon releasing him from the cage in World 3-2 or immediately after finding the two unnamed corpses in the Nexus. He is found on the second floor near the unnamed corpse. Killing him as soon as you release him has no effect on character or world tendencies.

When killed he will drop the following (plague and poison resist plate):

Note. If Yurt falls for any reason, you can quit and reload your game to find his Gloom Armor set next to his cage.

Strategies:

Melee Strategy

An easy melee exploiting the fact Yurt isn't initially hostile upon freeing him. He'll allow you to back stab him with impunity up to 3 times before turning hostile, so you can use this either to use the backstab knock away animation to push him off the tower or to kill him outright if your damage output is high enough.Note. If Yurt falls from backstabbing, you can quit and reload your game to find his Gloom Armor set next to his cage.

Ranged Strategy

This is a bit tricky as it requires you to backtrack up to the tower above him. Once you get back up however Yurt does not have enough range to shoot back, and if you're a good enough shot you can take him down in a hundred arrows or a few dozen spells.
Alternatively, let him out of his cage and then cast Evacuate. On return to the Nexus, he will not be there. Return to his area and he will still be walking around. Without dropping down to his level, shoot him with a Bow. He will charge at you, and fall off the edge.

Magic Strategy

The Poison Cloud spell can kill most NPCs in one hit if you wait out the duration and Yurt is no exception. After releasing Yurt one needs only to cast the spell and step into the the cage he once occupied to find a safe place to wait for the spell's effect to kill him. A short jaunt back up the elevator after Yurt has died will allow you to pick up your Gloom Armor. Also, you can cast Firestorm and kill him outright (tested with 24 Magic, Ring of Magical Sharpness, Monk's Head Collar and Kris Blade). Soulsucker will also kill Yurt in one hit.